Positive displacement casting system employing shaped electrode for effecting cosmetically perfect bonds

ABSTRACT

Methods and apparatus for positive displacement casting and/or for positive displacement bonding and, more particularly, for automatically forming, on a continuous, reproducible basis, fusion bonds devoid of structural, electrical and cosmetic defects between two or more workpieces by moving a heated electrode into the area to be bonded so as to uniformly heat and melt the portions of the workpieces to be bonded while, at the same time, displacing substantially all of the molten material from the area to be bonded into a storage area or reservoir surrounding the heated electrode where such molten material is maintained in its uniformly heated molten state, and then retracting the electrode so as to permit the molten material to return to the cavity formed by the electrode in the workpieces where such molten material is allowed to cool and solidify, thus forming a flawless bond between the workpieces-thermal or fusion bonds are made in accordance with the methods of the invention and with the apparatus of the invention by a combination of 1) elevated temperature levels sufficient to melt the material to be bonded, and 2) displacement of the molten material; as contrasted with more conventional techniques and/or apparatus which combine elevated temperature levels and pressure.

United States Patent 1191 Schenk, Jr. et a1.

1 1 POSITIVE DISPLACEMENT CASTING SYSTEM EMPLOYING SHAPED ELECTRODE FOREFFECTING COSMETICALLY PERFECT BONDS [75] Inventors: Raymond Schenk,,lr.,

Doylestown, Pa.; John A. Bruzas, Trenton, NJ.

[73] Assignee: Gould Inc., St. Paul, Minn.

[22] Filed: Jan. 21, 1974 [21] Appl. No.: 435,181

[52] U.S. Cl. 164/80; 29/204; 164/D1G. 1; 228/45; 228/58 [51] Int. Cl.'-I-l0lM 2/2 HOIM /3 B22D 19/00; B23K 1/12 [58] Field of Search 164/80,107, 108, 110,

164/D1G. 1; 29/486, 498, 491, 472.1, 204, 475, 494, 495; 228/45, 58;136/176, 134 R, 168; 219/78, 86

[4 1 Sept. 30, 1975 [5 7] ABSTRACT Methods and apparatus for positivedisplacement casting and/or for positive displacement bonding and,

more particularly, for automatically forming, on a continuous,reproducible basis, fusion bonds devoid of structural, electrical andcosmetic defects between' two or more workpieces by moving a heatedelectrode into the area to be bonded so as to uniformly heat and meltthe portions of the workpieces to be bonded while, at the same time,displacing substantially all of the molten material from the area to bebonded into a storage area or reservoir surrounding the heated electrodewhere such molten material is maintained in its uniformly heated moltenstate, and then retracting the electrode so as to permit the moltenmaterial to return to the cavity formed by the electrode in theWorkpieces where such molten material is allowed to cool and solidify,thus forming a flawless bond between the workpiecesthermal or fusionbonds are made in accordance with the methods of the invention and withthe apparatus of the invention by a combination of l) elevatedtemperature levels sufficient to melt the material to be bonded, and 2)displacement of the molten material; as contrasted with moreconventional techniques and/or apparatus which combine elevatedtemperature levels and pressure.

6 Claims, 17 Drawing Figures US. Patent Sept. 30,1975 Sheetlof 103,908,743

US. Patent Sept. 30,1975 SheetZof 10 3,908,743

US. Patent Sept. 30,1975 Sheet4of 10 3,908,743

US. Patent Sept 30,1975 SheetSof 10 3,908,743

U.S. Patent Sept. 30,1575 Sheet60f 10 3,908,743

US. Patent Sept. 30,1975 Sheet70f10 3,908,743

US. Patent Sept. 30,1975 Sheet 10 of 10 3,908,743

POSITIVE DISPLACEMENT CASTING SYSTEM EMPLOYING SHAPED ELECTRODE FOREFFECTING COSMETICALLY PERFECT BONDS RELATED APPLICATIONS RobertHolbrook Cushman, Ser. No. 435,157, filed Jan. 21, 1974.

Raymond L. Schenk, Jr., Ser. No. 435,178, filed Jan. 21, 1974.

Alan S. Keizer, Ser. No. 435,179, filed Jan. 21, 1974.

Robert Holbrook Cushman and Raymond L. Schenk, Jr., Ser. No. 435,169,filed Jan. 21, 1974.

Raymond L. Schenk, Jr. and Alan S. Keizer, Ser. No. 435,160, filed Jan.21, 1974.

Raymond L. Schenk, Jr., Robert Holbrook Cushman and Alan S. Keizer, Ser.No. 435,180, filed Jan. 21,

Kurt R. Stirner and Robert Holbrook Cushman, Ser. No. 435,172, filedJan. 21, 1974.

Raymond L. Schenk, Jr., John A. Bruzas and William E. Coville, Ser. No.435,182, filed Jan. 21, 1974.

John A. Bruzas and William Coville, Ser. No. 435,156, filed Jan. 21,1974.

Raymond L. Schenk, Jr. and William B. Hayes, Ser. No. 435,166, filedJan. 21, 1974.

BACKGROUND OF THE INVENTION The present invention relates in general tofusion casting, and/or to fusion bonding or thermo bonding of two ormore workpieces and, more particularly, to methods and apparatuscharacterized by their ability to automatically form, on a continuous,reproducible,

high speed, production-line basis, cast parts having a.

desired shape, as well as fusion bonds devoid of structural, electricaland/or cosmetic defects between two or more workpieces by a techniquehereinafter referred to as positive displacement casting. It will becomeapparent as the ensuing description proceeds that the term casting" isused herein in its broadest sense and encompasses the melting andshaping or reshaping of one or more parts into a single. unitarystructure which may or may not be composite with an unaltered workpiececomponent, all by and with the positive displacement system disclosedherein. Thus, the phrase "positive displacement casting is intendedherein to be generic to positive displacement bonding." In its principalaspects, the invention is concerned with improved methods and apparatusfor automatically moving a heated electrode through the portions of theworkpiece(s) to be cast or bonded so as to uniformly heat and melt thoseportions of the workpiece(s) to be cast or bonded while, at the sametime, displacing the molten material into a storage area or reservoirsurrounding the heated electrode where such material is maintained inits uniformly heated molten state while further movement of theelectrode into the workpiece(s) creates a cavity therein and,thereafter, retracting the heated electrode so as to permit the moltenmaterial to return to the cavity formed by the electrode in theworkpiece(s) where such molten material is allowed to cool and solidify,thus forming a flawless bond between the workpieces and/or casting oneor more workpieces in a predetermined shape or form.

In recent years, there has been an ever increasing trend toward, anddemand for. automation and mechanization in virtually all branches ofindustry. In many industries, typically including, but not limited to,the

battery making industry, it is often necessary to bond two or moreworkpieces together to form a unitary assembly wherein the bond ischaracterized by its structural strength and/or, in some instances, byexcellent characteristics of electrical conductivity. Various methodshave been devised for bonding such workpieces together including, merelyby way of example, welding, thermo-compression bonding, ultrasonicbonding, percussion welding. etc.

The particular technique selected has heretofore depended upon manyvariable parameters. including: 1) the sizes and/or shapes of theworkpieces; and 2) various characteristics of the particular materialsto be bonded which may vary widely in such areas as electrical and/orthermal conductivity characteristics, melting points, etc. Moreover, theparticular technique employed has often been dictated by physicallimitations in access to the region where the bonds are to be effected.Merely by way of example. in the battery industry it is often necessaryto bond two or more pieces of lead together at various points, in somecases internally and in other externally of a given battery cell. Lead.of course, is characterized by having a relatively low melting point onthe order of only 630F., as contrasted with, for example, steel whichhas a melting point on the order of 3,000 ,F. Moreover. where the leadworkpieces comprise battery straps, plates, terminal posts and/orintercell connectors, such as commonly employed in industrialmotive-power batteries, automotive batteries, and the like, it is oftendifficult to gain access to the parts to be bonded. Even where accesscan be obtained, one is normally limited in the amount of heat that canbe applied and in the types of reducing agents that can be utilized byvirtue of other components present in the area of the bond to beeffected such, for example, as the battery casing or cell jar which iscommonly made of rubber, the electrolytic acids present in or to beadded to the battery cells, the pasted positive and/or negative plates,the separators which are commonly made of microporous rubber, etc. Manyefforts hav e been made to devise improved bonding techniques which canbe universally applied for the purpose of bonding two or more workpiecestogether irrespective of the wide range of variable parameters mentionedabove. Moreover, consistent with the demands of industry today, numerousefforts have been made to devise bonding techniques which are capable ofautomation so as to enable automatic bonding of multiple workpieces asan integrated part of massproduction line and/or assembly linetechniques. Typical of the aforementioned approaches are those describedin US. Pat. Nos. 3,591,755, 3,608,809 and 3,706,126 of Robert HolbrookCushman, assigned to the Western Electric Company, and relating tomechanical-thermal-pulse continuous fusion bonding processes andapparatus which are based, at least in part, upon a combination ofapplied and controlled pressure and temperature to effect a desiredbond.

However, despite all such prior efforts which have met with varyingdegrees of success, certain industries have continued to employ the moretedious, timeconsuming, manual bonding techniques which have been knownand utilized for many years. Typical of these is the industrialmotive-power battery industry where lead-to-lead bonds are still almostuniversally made by hand-torching or hand-burning techniques employingoxyacetylene torches and/0r carbon burning tools. These techniquesrequire highly skilled artisans who are capable of forming satisfactorybonds only after considerable training and, even then. a relatively highpercentage of the bonds formed are not capable of meeting the rigorousquality control standards set by the battery industry. Typical of thetypes of difficulties encountered even by such skilled artisans are: 1)nonuniform heating of the interface between the parts to be bondedresulting in no bonding at all at some locations, and/or burn-out ofconnectors and/or other parts because of over burning," therebydestroying the connector or other parts; 2) actual damage to and- /ordestruction of the rubber casing or battery cover due to inadvertentdirect application of the flame or carbon tip thereto; 3) lack ofcontrol over, and resul-v tant nonuniformity of the depth of, bondpenetration into the parts to be bonded, thereby resulting in bondswhich are unsatisfactory from either or both of structural and/orelectrical conductivity characteristics; and 4) substantially completemelting of one of the two or more parts to be bonded accompanied byfailure to melt the surface ofa second of the pieces to be bonded,thereby resulting in a cold-knit between the properly and improperlymelted pieces.

As a direct result of the inability of certain industries-for example,the battery industryto utilize the aforementioned known automatic andsemi-automatic bonding systems. and the continued industry-wide relianceon hand-torching and/or hand-burning techniques, numerous disadvantageshave continued to plague such industries. More specifically: 1) variousindustries, at great expense to themselves, have had to continue toattempt to train personnel in the difficult, time-consuminghand-torching or hand-burning techniques; 2) a result of the relativelyhigh heat generated by such techniques, the use of low melting point,economical, lightweight plastic battery casings has been precluded; 3)the percentage of batteries and/or battery cells rejected because ofunsatisfactory bonds has remained high; and 4) the number of batterieswhich have passed rigorous quality control tests and/or procedures whilehaving latent defects in the bonds has been unacceptably high, resultingin customer dissatisfaction because of the presence of leakers,particularly in the battery post/intercell connector, as well as anextremely objectionable phenomenon known in the art as electro-capillaryaction wherein battery electrolyte is actually pumped out of the batterycell through minute passages passing through the positive batterypost/connector interface where the bond is defective, thereby not onlyweakening the cell affected and decreasing its life and usefulness, butoften creating a direct short which drains the battery and which oftencauses corrosion and irreparable damage to other equipment in theimmediate area.

OBJECTS OF THE INVENTION It is a general aim of the present invention toprovide improved bonding and/or casting methods and apparatus whichovercome all of the foregoing disadvantages and which are characterizednot only by their dependability and reliability in operation, but, alsoby their ability to continuously reproduce successive bonds havingsubstantially identical characteristics and which meet the rigorousquality control standards set by the industry. More specifically, it isa principal aim of the invention to provide new and novel methods andapparatus for forming metal-to-metal bonds which. when applied to thebattery making industry, substantially eliminate. if not completelyeliminate, the danger of leakers and/or electro-capillary actionresulting from non-uniform bonding of the battery post/intercellconnector interface.

Another of the general objectives of the present invention is theprovision of improved bonding and/or casting methods and apparatus whichcan be readily introduced into existing production and/or assembly lineswith only minimum revisions to, and interruption of. such lines.

A more detailed general objective of the present invention is theprovision of improved bonding and/or casting methods and apparatus whichare capable of bonding motive-power battery posts to intercellconnectors with a high level of quality and repeatability, yet atreduced manufacturing costs.

A further object of the invention is the provision of improved methodsand apparatus for producing bonds between two or more components whereineach bond produced is characterized by the uniformity of the bondthrough any desired, preselected depth into the workpieces, therebyproducing bonds which, in the battery field, are devoid of leakers anddevoid of electro capillary action.

It is a general aim of the present invention to provide an improvedelectrode configuration for use in positive displacement castingtechniques and which insures the production of bonds characterized bytheir smooth, flat and regular or symmetrical disk-likeconfigurations-i.e., bonds which are devoid of pits, crevices and/orcold collars and which have a cosmetic appearance comparable to the mostperfectly formed hand-torched or hand-burned bonds heretofore attainableby highly skilled artisans.

SUMMARY OF THE INVENTION The present invention pertains to methods andapparatus which are intended to overcome all of the aforementioneddisadvantages and to provide a system which is capable of performingsuccessive fusion casting and/or fusion bonding operations on arelatively high speed, mass production or assembly-line basis, yet whereeach bond formed is essentially devoid of flaws or imperfections and iscomparable in quality to the most prefectly formed hand-burned orhand-torched bond heretofore attainable by even the most skilledpersonnel. To accomplish this, the present invention contemplatesmethods and apparatus wherein a uniquely formed heated ram-likeelectrode is moved co-axially through a reservoir defining means which,in the exemplary forms of the invention, comprises a coaxial barrelsurrounding the electrode and defining therebetween an annularreservoir. The reservoir defining meanse.g., the barrelis first bottomedon one of the elements to be bonded in a position co-axial with the axisof the bond to be formed. Thereafter, the ramlike electrode is movedaxially through the reservoir defining means into engagement with theworkpiece or workpieces to be bonded where the heat developed serves toconvert the solid workpiece(s) to a molten state in the area selectedfor the fusion bond. Continued axial advance of the electrode serves toprogressively melt the portions of the workpieces along the axis of thebond area, which axis, of course, coincides with the axis of theelectrode, and the molten material thus formed is displaced by theelectrode in an annular column surrounding the electrode and within thereser, voir defined between the electrode and the selected reservoirdefining means.

When the ram-like electrode reaches the limit ofits advance movement, alimit that may be adjusted by the operator to provide for a bond of anydesired depth, a short dwell period is provided to insure uniformheating of those portions of the workpieces immediately adjacent thecavity formed therein by displacement of molten material, as well as toinsure uniform'heating of the molten material surrounding the electrodeand confined within the reservoir. Upon conclusion of such dwell period,the ram-like electrode is retracted from the workpieces and is movedaxially through the reservoir defining means to a position out ofcontact with the molten material. As a result of such axial retractionof the electrode, the molten'material is free to return to the cavityformed in the workpieces during the advance movement of the electrode,where such material is permitted to cool and solidify, thus forming auhi form fusion bond between the workpieces along the entire axis ofelectrode movement therethrough. Finally, the reservoir definingmeans'e.g., the barrel co-axial with the electrode-is retracted from itsbottomed engagement with the workpieces, and the bond cycle is complete.

When dealing with workpieces formed of conductive metals, the activatingcircuit for the system is preferably from a suitable power source,through the movable electrode, through the conductive metal workpieces,through the reservoir defining means, and back to the source. The powersource may be either continuous or pulsating. When dealing withnon-conductive workpiece materials, the movable ram-like electrode maysimply comprise or contain a suitable resistance element or the likecapable of attaining and maintaining a desired temperature levelsufficient to melt that portion of the workpiece material which is to bedisplaced and subsequently returned to effect the desired fusion bond.

While the present invention is susceptible of various modifications andalternative forms, specific embodiments thereof have been shown by wayof example in the drawings and will herein be described in detail. Morespecifically, the invention will hereinafter be described in connectionwith equipment for forming leadto-lead bonds and/or for positivedisplacement casting a of lead, techniques that are particularlysuitable for use in the industrial motive-power battery industry and,for

that reason, the exemplary forms of the invention are described inconnection with the making of such batteries. In its broadest aspects,however, it will be understood as the ensuing description proceeds thatthe invention may find many other applications outside of the batterymaking industry, outside of lead-to-lead fusion bonding techniques and,indeed, outside of metalto-metal fusion bonding techniques. Therefore,it should be understood that it is not intended to limit the inventionto the particular forms disclosed, but, on the contrary, the intentionis to cover all modifications, equivalents and alternatives fallingwithin the; spirit and scope of the invention as expressed in theappended claims. A:

These and other objects and advantages of the present invention willbecome morereadilyapparent upon 6 readingthe ensuingdetailed'description of the invention and upon reference to theattachedv drawings.

DESCRIPTION OF THE DRAWINGS FIG. 1 isa fragmentary exploded perspectiveview. here illustrating the various components present in a conventionallead-acid storage battery cell of the type commonly manufactured todayand for many years past in the industrial motive-power battery industry:

FIG. 2 is a fragmentary perspective view, here illustratingthe-conventional and well-known technique of bonding an intercellconnector with the use of a handheld carbon burning tool and a hand-heldsource of supplemental lead.

FIG. 3lis a vertical side elevation, partly in section, of aconventional battery cover, post, bushing and intercell connectorassembly, here illustrating the parts prior to a hand-torching orhand-burning bonding operation.

.FIG. 4 is a perspective view of a portion of av positive displacementcasting system embodying features of the present invention, hereillustrating an industrial motive-power battery disposed on a conveyorbeneath a bonding head positioned to automatically effect a bond betweena lead battery post of one battery cell and an intercell connector.

FIG. 5 is a fragmentary perspective view taken generally at right anglesto the view shown in FIG. 4 and here depicting other portions of theapparatus.

FIG. 6 is a plan view of the exemplary apparatus shown in FIG. 4, heredepicting the bonding head over one conveyor belt and abatterypositioned on the adjacent conveyor belt in readiness for abonding operation.

FIG. 7 is an elevational view taken substantially along the line 7-7 ofFIG. 6, here depicting the bonding head in solid lines disposed over abattery carried by the le'ft-handconveyorand in phantom lines over abattery carriedby the right-hand conveyor.

FIG. 8 is a perspective view of the front of a control console utilizedwith the apparatus of the present invention, here depicting the consolewith its lower door open to expose the drawer containing certain of theelectrical controls for the system.

FIG. 9 is an exploded perspective view, here illustrating particularlythe relationship between a batterycover, post, bushing and intercellconnector embodying features of the present invention.

FIG. 10 is an elevational view, partly in section, similar to FIG. 3,but here illustrating the various components of a battery post/intercellconnector assembly embodying features of the present invention, againdepicting the parts prior to a bonding operation.

FIGS. 11a through He are fragmentary, enlarged, simplified, and somewhatdiagramatic side elevational views, partly in section, here depictingthe sequence of operations in a typical positive displacement castingoperation embodying features of the present invention; FIG. 11adepicting the battery components to be bonded with the bonding headdisposed above such components;

FIG. 11!) illustrating the bonding head properly located and locked inposition in-readiness to initiate a bonding operations FIG. 11cillustrating the component parts of the system with the bonding ram-likeelectrode partially advanced into the workpieces to be bonded, and withthe molten lead formed through this stage of the procedure having beendisplaced into surrounding relationship to the ram;

FIG. 11d illustrating the component parts of the system with theram-like electrode fully advanced into the workpieces to be bonded andwith the molten lead formed having been displaced into surroundingrelationship to the ram; and,

FIG. 11e depicting the component parts of the system with the bondinghead still in its down position but with the ram-like electroderetracted and with the molten lead having been returned to the cavityformed by the ram in the workpieces and having cooled and solidified toform a finished bond.

FIG. 12 is a perspective view of a completed bonded assembly comprisinga battery post, bushing and intercell connector, but wherein theresultant bond is defective and characterized by the presence of coldcollars, cracks and crazing, and the presence of a concavity orsaucer-like configuration on the upper surface of the resultant bond,all of which are undesirable characteristics for intercell connectorassemblies, particularly on industrial motive-power batteries.

FIG. 13 is a fragmentary perspective view of a portion of a battery,here depicting, in both the bonded and unbonded states, batterypost/bushing combinations both with and without intercell connectors.

/ THE ENVIRONMENT OF THE INVENTION As hereinabove explained, the presentinvention will be described herein in connection with methods andapparatus which find particularly, but by no means exclusive,application in the industrial motive-power battery industry.Accordingly, and as best seen by reference to FIGS. 1, 2 and 3conjointly, there have been depicted fragmentary portions of a typicalindustrial battery, generally indicated at 50 in FIG. 2, which is herecomposed of a plurality of individual battery cells 51. Such batteriesmay vary widely in size, configuration and electrical characteristics,and may, merely by way of example, range upwards of several feet inlength, heighth and width and weigh upwards of seveal tons. Conversely,such batteries may be relatively small and may be capable of beingtransported by hand.

Referring more specifically to FIG. 1, a conventional battery cell 51has been depicted in partially exploded form so as to expose most of thevarious battery components contained therein. Such components normallyinclude a cell casing 52, commonly called a jar, and cover 54, both ofwhich have heretofore conventionally been formed of high impact rubber.Contained within the cell casing 52 are a group of negative plates 55, agroup of positive plates 56, and a group of separators 58. The negativeplates 55 and positive plates 56 of the exemplary cell 51 comprise castlead grids into which selected chemical pastes, or active materials, areinserted. Generally, a negative plate 55 may contain a paste consistingofa spongy lead material containing an expander to maintain the spongycondition, while the positive plates 56 may contain a paste consistingof lead oxide, sulfuric acid and water mixed to a putty-likeconsistency. After the pastes have been applied to the respective grids,the grids are dried. The positive plates 56 are normally wrapped withfiberglas or the like (not shown) to insure retention of the activematerials, and each positive plate is then inserted into a plasticprotective envelope, as best indicated at 59 (FIG. 1 The separators 58are preferably formed of microporous rubber which is temperature andacid resistant. and are generally flat on the side adjacent the negativeplate and grooved on the side adjacent a positive plate. Such separators58 serve as insulators between the interleaved positive and negativeplates, although they are sufficiently porous to permit free passage ofelectrolyte therethrough.

After casting of the positive and negative plates, application of theactive materials thereto, drying, and wrapping of the positive plates,positive and negative groups or assemblies of plates are formed,commonly by welding the lug portions 55a, 56a of the plates to batterystraps and/or battery posts. As here shown, the negative plate lugs 55aare welded to a battery strap 60 integral with a pair of verticallyupstanding, negative battery posts 61, while the positive plate lugs5611 are welded to a similar battery strap 62 integral with a pair ofvertically upstanding positive battery posts 64. The thus assemblednegative and positive plate groups are then interleaved with oneanother, there being a separator 58 between each positive and negativeplate, and the entire assembly is inserted into the cell casing or jar52 on top of a sediment bridge (not shown). A protective element 65,which may be made of plastic, is placed on top of the plate assembly soas to prevent: 1) foreign materials from entering the cell; 2) damage tothe internal cell components by careless use of hydrometers orthermometers; and 3) moss shorts between the positive and negativeplates. The high impact rubber cover 54 is then positioned on top of thejar or casing 52, with the posts 61 and 64 passing through lead bushings66 molded in place in the cover, and the cover is secured to the jar bymeans of a hot, pliable, asphalt based compound. Normally at this stageof the assembly operation, the battery posts 61, 64 are bonded to therespective bushing inserts 66 by a hand-burning or hand-torchingtechnique, electrolyte is added to the battery cell through a fillopening 68 adapted to be closed by a screw-threaded tap 69, and the cellis then repetitively charged and discharged to assure proper capacityand quality.

Once the cells 51 have been assembled, charged and inspected, they arethen ready to be assembled in various configurations to provide acomplete battery to meet specific requirements of a customer or ultimateuser. In such assembly, multiple cells are inserted into a steel batterycasing 70 (FIG. 2) and interconnected in accordance with therequirements and specifications of the customer or user. Suchinterconnections commonly entail the use of lead intercell connectors 71which bridge the space between battery posts of opposite polarity inadjacent cellsi.e., the positive posts of one cell are coupled to thenegative posts of an adjacent cell. Referring to FIGS. 2 and 3, it willbe observed that each intercell connector 71 is designed so that one endthereof sits on and surrounds a bushing 66 associated with a negativepost 61, while the opposite end thereof sits on and surrounds a bushing66 associated with a positive post 64. The workman then bonds theconnector 71 to the post/bushing combination by a conventionalhand-burning or hand-torching technique. Thus, referring to FIG. 2, itwill be observed that the workman is utilizing a hand-burning techniquein which he is holding a carbon burning tool 72 in his right hand and arod oflead bar-stock 74 in. his left hand. The arrangement is such thatthe carbon burning tool supplemental lead rod 74 so as to providesufficient molten lead to fill the entire cavity within the connector 71defined by the edge 75 and surrounding the postlbushing combination.Indeed, the workman will commonly place a conventional mold (not shown)about the work area so as to permit the formation of a raised,button-like bond, as best indicated at 76 in FIG. 2.

It should be understood, that while it would be possible to create theaforementioned bond 76 in a single hand-burning or hand-torchingoperation by applying the tool 72 or torch to the assemblage of parts asshown in FIG. 3, the operation is most normally conducted in twostagesfirst bonding the post/bushing combina- -tion and later bondingthe connector 71 to the previously bonded post/bushing combination. Onereason for such two-stage bonding or torching procedure is simply thatit is desirable that a permanent bond be created between the post 61(64) and bushing 66 immediately after assembly and prior to introductionof electrolyte into the cell so as to prevent acid or other foreignmaterials from becoming lodged in the interface between the post and thebushing.

It will be immediately recognized by those skilled in the art that thehand-burning and/or hand-torching operations herein described have manydisadvantages and are frought with dangers. Such procedures are slow,and require skilled personnel to cary them out. As lead is melted andpuddled, it tends to cover the surfaces of the parts to be bonded, andextreme care must be taken to insure that all of the mating surfaces orinterfaces to be bonded are uniformly heated and renderedmolten-otherwise, molten lead contained within the puddle will tend toadhere to a surface which has not been raised to a sufficiently hightemperature level, thereby producing an undesirable cold knit ratherthan a sound molecular fusion bond. Moreover, failure to obtain uniformheating and melting may result in undesirable crevices or minutepassages passing through the interface of the parts being bonded, thuscreating Ieakers and giving rise to the danger of electro-capillarypumping action at the positive post. And, of course, if extreme care isnot taken, it is relatively easy to overheat the parts. When thisoccurs,'the entire peripheral porhas been illustrated an exemplaryapparatus, generally indicated at 100 in FIGS. 4 7, for carrying out thepresent invention. As here shown, the exemplary appara tus 100 includesa positive displacement bonding head, generally indicated at lI, carriedby an overhead suspension system. generally indicated at 102, formovement over and with respect to one or moe batteries 50 carried on apair of parallel. spaced apart, floormounted conveyors 104, 105. Theconveyors 104. 105 may be power driven by any suitable means (not shown)and, to permit of ready control thereover. the bonding head 101 isprovided with a pair of operator controls 106, 108 (best illustrated inFIGS. 4 and 5) by which the operator can activate the conveyor drivingmeans to move a selected conveyor 104, 105 in either a forward orreverse direction, or to stop-a selected conveyor in a desired locationwith a battery 50 disposed beneath the bonding head 101. Preferably theoperator control 106 forms part of a suitable activating circuit (notshown) for conveyor 104, while the control 108 forms part of anactivating circuit for conveyor lightweight materials such as plastic inthe formation of I cell casings and/or covers because such materialscommonly have much lower melting points than the hard impact rubberheretofore used.

POSITIVE DISPLACEMENT BONDING IN ACCORDANCE WITH THE INVENTION A.General Organization of Exemplary Apparatus Referring now to FIGS. 4through 9 inclusive, there 105. To facilitate placement of batteries 50on, and re- .moval from, the conveyors, the batteries may be positionedon pallets 109 or the like which can be readily moved from place toplace by conventional fork-lift trucks.

A-l. X-Oriented Movement In order to permit of facile movement of thebonding I oriented direction (along the line of conveyor move-' ment asindicated by the arrows in FIGS. 4 6). To accomplish this, the overheadsuspension system 102 includes a pair of parallel. spaced apart beams110, 111

(best illustrated in FIGS. 4 and 12) which extend transv versely acrossboth conveyors 104, and which are connected at their opposite ends bycross beams 112, I14; (FIG. 6) the beams 110, 111, 112 and 114 defininga generally rectangular support structure (FIG. 6). Vertically disposed,upright stanchions I15 and 116 are permanently affixed at their upperends to the cross beams 112, 114 respectively, and are mounted 'on thefloor outboard of the conveyors 104, 105. The beams 1 10, l l 1respectively support guide rails or tracks 1 18, 119 which are parallelto "the'beams and also extend transversely across the conveyors 104,105. A carriage assembly, generally indicated at- 120 in FIGS. 4 and 7,is provided with suitable bearing sleeves 121 (FIGSL4 and 12) mounted insurrounding relation to the rails 118, 119, thereby permitting slidablemovement of the entire carriage assembly 120 in an X-oriented directionalong the rails. Suitable lubricating means (not shown) may be providedso as to minimize friction and thereby permit ease of movement of thecarriage assembly 120 along the rails A-2. Y-Oriented Movement Forthepurpose of permitting movement of the bonding head 101 in aY-oriented directioni'.e., along the path of movement of the conveyors104, l05-the carria'ge assembly 120 is provided with a pair of dependingsupport beams 122, 124 (best illustrated in FIG. 4) which here serve tosupport Y-oriented tracks or guide rails 125, 126, respectively. Asub-carriage assembly. generally indicated at 128, is slidably supportedon the guide rails 125, 126 by means of bearing sleeves 129.

A-3 Z-Oriented Movement In carrying out the present invention, provisionis made for enabling vertical movement of the bonding head 101 along aZ-oriented axis as viewed in FIGS. 4, 5 and 7. To this end, the variousoperating parts of the bonding head 101 are carried by a base plate 130which is secured to the lower ends of a pair of vertically disposedsupport shafts 131, 132, such shafts passing upwardly through respectiveones of a pair of bearing sleeves 134, 135 rigidly secured to a plate136 which forms the undercarriage of sub-carriage assembly 128. Theupper ends of the shafts 131, 132 have enlarged collars 138, 139 (FIG.6; best illustrated in FIG. 14) respectively affixed thereto which serveas stops engageable with plate 136 to limit downward movement of thebonding head 101.

For the purpose of permitting the bonding head 101 to float" duringperiods between bonding cycles and during movement of the head by theoperator. and to further permit automatic movement of the operatingparts of the bonding head during a bonding cycle, the illustrativeapparatus is provided with a series of fluidoperated, preferablypneumatic, piston/cylinder combinations 140, 141, 142, the specificfunctions of which are described in considerably greater detail in theaforesaid copending applications of Robert Holbrook Cushman, Ser. No.435,157, and Raymond L. Schenk, Jr., Ser. No. 435,178. Those interestedin such detailed descriptions are referred to the aforesaid copendingapplications. For the purpose of the present description of the generalorganization of parts for the exemplary apparatus, it will suffice tosay that the opposite sides of the piston within piston/cylindercombination 140 are pressurized so as to balance the weight of thecomponents carried by base plate 130 and which comprise the bonding head101, thereby permitting the head to float at whatever height or level itis positioned in.

A-4. Operator Controlled Positioning of Bonding Head The arrangement issuch that when the operator wishes to move the bonding head 101 into aposition in readiness to initiate a bonding cyclefor example, inreadiness to bond a battery post/intercell connector combination such asgenerally indicated at 144 in FIGS. 4 and 5-it is merely necessary thathe first activate the control 106 for conveyor 104 (or, alternatively,control 108 for conveyor 105) to generally cate a battery 50 beneath thebonding head 101. Having generally located a battery relative to thehead, the operator next grasps one of the handles 145 projectinglaterally from the base plate 130 and shifts the bonding head 101laterally in either or both of an X-oriented and/or Y-oriented directionuntil the bonding ram assembly, generally indicated at 146 in FIGS. 4,5and 7, is accurately centered over the particular battery postlintercellconnector combination 144 to be bonded.

The operator then needs only push downwardly on the handle so as to urgethe bonding head 101 the ram assembly 146 downwardly from the positionshown in FIG. 7 to the position such as shown in FIGS. 4 and 5 wheretheparticular battery post to be bonded projects co-axially upward into thebonding ram assembly 146 when the latter is bottomed on the intercellconnector to be bonded. The operator is now ready to initiate a bondingcycle for the particular post/connector combination 144 located underthe bonding ram assembly 146 and, when the bond is completed, thebonding head 101 will automatically move upward to the position shown inFIG. 7. The operator then again grasps the handle 145 and moves thebonding head 101 in either an X- or Y- oriented direction to a positionover the next post/connector combination 144 to be bonded, and againrepeats the foregoing operation.

A-S. Typical Battery Post, Bushing and lntercell Connector to Be BondedReferring next to FIGS. 9 and 10, there have been illustrated details ofa typical organization of battery components particularly suitable forbonding in accordance with the present invention. More specifically,there is depicted a battery post/intercell connector combination 144which consists of an upstanding lead.

battery post 148, a lead cover bushing 149 adapted to be molded directlyinto a battery or cell casing 150 (which may conveniently be made ofplastic, hard impact rubber, or any other suitable material), and a leadintercell connector 151. The lower end of battery post 148 is, asheretofore described, affixed to, or integral with, a battery platestrap 152 which serves to interconnect a plurality of battery plates oflike polarity-either positive plates or negative plates. The arrangementis such that, when assembled prior to bonding as shown in FIG. 10, thebattery post 148 passes co-axially upward through the lead bushinginsert 149 and cover 150. The opposite ends of the lead intercellconnector (one such end being visible in FIGS. 9 and 10) are eachprovided with a vertically disposed opening or passage 154 having adiameter sufficiently large to permit the connector 151 to be positionedin co-axial surrounding relation to an upstanding flange 155 formed onthe bushing 151, with the lower surface of the connector in directlead-to-lead contact with a horizontal or radial flange- 156 formed onthe bushing.

To insure concentricity of the parts and, at the same time, to providefor sound electrical therebetween, the lead battery post 148 may beprovided with two or more slightly raised locating ribs or projections(one such rib having been illustrated at 158 only in FIG. 9), which ribshave a slightly larger diameter than the inside diameter of the bushing149. However. because of the characteristic of softness inherent withlead, the

battery post may be relatively easily force-fit into the bushing 149,and the presence of such ribs thus serves to insure good electricalcontact between the post 148 and bushing 149 while, at the same time,serving to center the post within the bushing.

ln keepng with the present invention, the intercell connector isprovided with an upstanding peripheral bond, while the upstanding collar159 on the connector serves as a locating means to insure properpositioning of the ram assembly 146 relative to the post/connectorcombination 144 to be bonded and, also, the collar 159 serves as asource of lead for the bond and a dam to confine the molten lead formedinitially in the bonding operation.

In carrying out the invention, the battery post 148 is designed toprovide all of the surplus lead required to effect a completed bondsuch, for example, as the bond shown at 161 in FIG. 5. To this end, itwill be observed that the illustrative battery post 148 projectsupwardly substantially above the upper surface of the connector locatingcollar 159 and, when the lead defining the up wardly projecting portionof the post is meltedduring a bonding cycle, such lead provides all ofthe molten material necessary to fill the annular cavity .within theconnector opening 154 and defined between the. post 148 and connector151. The particular height of the post 148 may vary since the amount ofthe lead supplied will be a function of both the height and the diameterof the post 148, while the amount oflead'required to form a desired bondwill be a function of the size of the connector opening 154 and thedesired height of the finished bond. However, it will be readilyapparent to those skilled in the art upon comparison of a conventionalpost/bushing/connector combination suchas shownin FIG. 3 with oneembodyingthe features of the invention such as shown at 144 in FIG. 10,that the novel assemblage of parts provided by the invention willeliminate the need for any separatesource of lead such, for example, asthe hand-held lead bar-stock 74 (FIG. 2) which has heretofore beenrequired in handburning and/or hand-torching operations.

A-6 Operator Controls In order to facilitate an'understanding of theensuing description, the various controls that are provided for theoperator and the location of such controls will be briefly described.During a normal seriesof bonding operations on a given battery orseriesof batteriesrthe operator will be required to handle only a'fewcontrols. These controls are, for the most part, mounted oneither thebonding head 101 or on the carriage assembly 120. Thus, as bestillustrated in FIG. 5, there are two operator controls mounted on thebonding head 101 in addition to the conveyor controls 106, 108previously described. These two additional controls include a controlbutton 162 which serves to activate a number of conventionalpneumatically actuated clamps ('not shown) that are mounted on thecarriage assembly and which serve to engage the X-oriented and Y-oriented rails 118, 119 and 125, 126 respectively, to lock the carriageassembly 120 and sub-carriage assembly 128 in position during a bondingcycle. At the same time, actuation of control button 162 serves toincrease the pressure on the upper end of piston/cylinder combination soas to move the electrode 164 (FIGS. 11a lld) contained within the ramassembly 146 downwardly into engagement with the top of a battery post148. The second control mounted on the bonding head 101 is indicated at165 in FIG. 5 and serves only to pressurize the bottom side of thepiston/cylinder combination 140, thereby allowing the operator torapidly move the bonding head 101 upwardly in a Z-oriented direction inthe event that rapid removal of the head from the battery is requiredfor any reason.

Dependingfrom the carriage assembly 120 is a small control console 166which is provided with a number of additional controls and indicatorlights, These controls include a bond initiate button 168, actuation ofwhich isrequired in order to turn bond power to the electrode l64on, andan emergency stop" control 169 which may be actuated by the operator inthe event of some emergency such as broken water line, severe arcing,fire or other similar emergency which requires turning the entire systemoff quickly. Similarly, there is provided a current abort" switch 170which permits the operator to turn the power supplied to the electrode164 off at any time he desires and for any reason. Indicator lights 171,172, 174 and serve various functions: light 171 indicates simply that a)the system is in condition'for locating movement of the carriageand/orsub-carriage assemblies 120, 128 and b) the operator can move thebonding head 101 in X-, Y- and/or Z-oriented-directions to locate thehead relative to the next post to bonded; light 172 indicates when theelectrode 164 is locked in its down position in readiness to bond; light174 indicates that power is on to the electrode 164 and a bonding cycleis underway; and, light 175 is simply a fault indicating light used toindicate that some fault has been detected by the monitoring portion ofthe system. When such a fault is detected, the monitoring portion of thesystem will serve to render the system inoperative until such time asthe operator ascertains what the problem is. At that time the operatorcan activate control button 176 which is simply a reset control thatserves to clear the memory of the computers (not described in detail)and permit continued operation of the system. Once the system has beenreset, the operator may take whatever steps are required to correct thefault before proceeding with the next bonding cycle. Referring to FIG.4, it will be observed that, for the convenience of the operator, thecontrols 162, 165 and the small control console 166 are all duplicatedon the opposite side of the equipment, thereby enabling the operator tohandle the bonding head 101 from either side of the conveyor.

The computer memory banks and related electronic equipment are containedwithin control panel and electronic console 178, best illustrated inFIG. 8. The particular electronic controls do not form an essential partof the present invention and, therefore, will not be described herein indetail. Rather, it should suffice for purposes of an overallunderstanding of the general organization of the apparatus and controlfunctions available, to simply point out certain of the controlsprovided. Thus, the console 178 includes a power OFF switch 179 and apower ON switch 180 which includes an ON indicator light. Similarly,there is provided a bond power OFF switch 181 and bond power ON switch182, the latter again including an indicator light. Disposed betweenthese two sets of power switches is a conventional milliammeter 184capable of displaying either power readings in watts or temperature, orcurrent readings in amperes, dependent upon the position of toggleswitch 185 mounted on the front of the lower console drawer 186.Conventional res'ettable digital display counters 188, 189 are providedfor indicating, respectively, the total number of bond cycles effectedby the apparatus, and the total number of bond cycles completed in agiven period of time such, for example, as per shift, per day or perweek. The mobile console 178 further includes a fault indicating light190 and reset button 191 which correspond to and duplicate the controls175, 176 shown in FIG. 5.

In order to permit presetting of the system so as to enable operationthereof within selected parameters, the mobile control console includesa number of rheostat type switches on the front of drawer 186. Theseinclude: a switch 192 for setting the amount of power to be provided tothe system; a switch 194 which sets the dwell period during which theheated electrode remains heated after it reaches its maximum penetrationinto the bond area; a switch 195 for setting the length of the coolperiod during which the molten material is permitted to cool after theelectrode 164 has been retracted but before the ram assembly 146 israised; and switches 197, 198, 199 and 200 for setting such othervariable parameters as the length of a bond cycle and the currentsetting for the electrode. These latter switches comprise part of themonitoring system and are related to indicator lights 201, 202, 204 and205 on the console which serve to indicate when a fault condition hasarisen requiring the operator to reset the system.

B. Positive Displacement BondingSequence of Operations Referring next toFIGS. 11a lle, there will be described a typical sequence of steps inmovement of the ram assembly 146 during a positive displacement bondingoperation pursuant to the present invention.

In keeping with the invention, provision is made for establishing areservoir surrounding the area to be bonded, advancing the heatedelectrode 164 through the reservoir and into and through the area of theworkpieces to be bonded so as to melt those portions of the workpiecesto be bonded and to displace the molten material formed into thereservoir, thereby insuring accurate control of the depth of penetrationinto the bond area, uniform heating of the surrounding unmelted parts ofthe workpieces, and uniform heating of the displaced molten materialcontained within the reservoir, and for thereafter retracting theelectrode so as to permit the displaced molten material stored in thereservoir to return to the cavity formed by the electrode in theworkpieces, where the material is permitted to cool and solidify. Toaccomplish this, and as best illustrated in FIGS. 11a and 111;, thelower end of the ram assembly 146 includes a central ram 205 having aninternal threaded bore 206 into which is threaded an adapter 208. Theadapter 208 serves to removably support the electrode 164 which isthreaded thereon. Preferably the ram 205 is formed of highly conductivematerial such as copper, while the adapter 208 and electrode 164 can beformed of various materials, some of which are hereinafter described.

In order to form a reservoir into which the molten material fomed can bedisplaced, the lower end of the ram assembly 146 includes a barrel 209formed of conductive material and which forms the outer member of theram assembly. The arrangement is such that the ram 205 and electrode 164are capable of axial movement through the barrel 209 and are insulatedfrom the barrel by means of a ceramic liner or sleeve 210. The lower endof the barrel 209 has affixed thereto a suitable conductive locating andretaining ring 211 which can be readily removed and replaced when theneed arises-for example, in the event of wear. Excellent results havebeen attained with the present invention by forming the locating andretaining ring 211 from beryllium copper alloy. A suitable annularinsulating collar 212, preferably made of phenolic plastic, ispositioned within the lower end of the barrel 209 and ring 211 and.together with the ceramic sleeve 210, prevents direct current flow fromthe electrode 209 and/or ram 205 through the molten material to thebarrel 210 and ring 211. The locating and retaining ring 211 serves anumber of functions. Thus, the ring 211 is provided with an inwardlyextending tapered radial flange that serves to retain the stackedannular insulator 212 and ceramic sleeve 210 in position. In addition.the lower surface of the ring 211 serves a locator to facilitate inaccurate positioning of the ram assembly 146 about the upright flange159 on the connector 151. Finally, the ring serves to complete a currentpath from the lead parts back through the conductive barrel 209.

Referring now more specifically to FIG. 11a, it will be observed thatthe ram assembly 146 is shown in solid lines somewhat above thepost/connector combination 144-i.e., in a position comparable to thatshown in FIG. 7and, in phantom lines in a downward position engaging theintercell connector 151i.e., in a position comparable to that shown inFIGS. 4 and 5. Thus, it will be understood that in order to move the ramassembly 146 from the solid line position of FIG. 11a to the phantomposition shown therein (at which point the electrode 164 will still bepositioned well above and out of engagement with the battery post 148),it is simply necessary for the operator to press downwardly on thehandle (FIG. 5) of the bonding head 101 in the manner previouslydescribed, thus forcing the head down and causing the locating ring 211to pilot about the upright flange portion 159 of the connector. When thelocating ring is properly positioned with respect to the connector, itwill engage the radial shoulder 160 on the connector and complete anelectrical connection therebetween. Because of the presence of thelocating collar 159 on the connector, in the event that the ram assemblyis misaligned with respect to the post/connector combination 144, thering 211 will engage the top of the collar and will not seat properly, acondition that will be readily apparent to the operator. In this event,the operator need only shift the bonding head 10] slightly in an X-and/or Y-oriented direction(s) until proper concentricity is achieved,at which point the opening in the ring 211 will permit further downwardmovement of the ram assembly until it reaches its proper downwardposition.

At this point in the operating cycle, the operator, having manuallypositioned the bonding head 101 and ram assembly 146 in properorientation with respect to the battery post/connector combination 144to be bonded and having observed that such proper orientation has beenachieved, is now ready to initiate a bond ing cycle. To this end, theoperator will first engage the clamp button 162 (FIG. 5) on the bondinghead, thereby serving to activate the pneumatic clamps (not shown) whichwill lock the carriage and sub-carriage assemblies 120, 128 in positionwith respect to the rails l 18, 119 and 125, 126, thereby preventingfurther X or Y movement of the bonding head. After a short time delay,pressure will be applied to the upper end of the piston/cylindercombination 140 (FIG. 4) which will serve to move the ram 205 andelectrode 164 downwardly into the position shown in FIG. 1112 where theelectrode 164 engages the top of the battery post 148.

At this point, the indicator light l72on control console 166 (FIG. willbe illuminated to indicate that the ram 205 is in position and theoperator can initiate the next step of the bonding cycle.

When the operator observes that light 172 is illuminated indicating abond ready condition, he then will engage the bond initiate button 168which'serves to complete an energizing circuit for the electrode 164.Referring to FIG. 11b, current will besupplied to the ram 205 from asuitable power source (not shown) and will be transmitted from the ram205 through the adapter 208 to the electrode 164 which serves as aresistance element that is heated to a level sufficient to rapidly meltthese portions of the lead components that it comes into engagementwith. The current path thus passes from the electrode through thebattery post 148, the lead bushing 149, the intercell connector 151, theberyllium copper locating and retaining ring 211, and back through theconductive barrel 209 to the power source. x

As current begins to flow through the foregoing circuit, the electrode164 is heated to a level'sufficient-to melt the lead battery post and,as a consequence, the ram 205 will start to move downwardly through theram assembly 146 under the influence of the pressurized piston/cylindercombination 140. Referring'next to FIG. 110, it will be observed thatthe electrode 164 has moved downwardly a's'ufficient distance to meltall of the upwardly projecting portion of the battery post 148 and, atthis stage of the cycle, the electrode has begun to melt the innerperipheral edge of the raised locating collar 159 on the connector.Moreover, the molten lead thus formed has been displaced laterally intoan annular upstanding column as best indicated at 214 in FIG. 11c withthe molten lead being disposed in the annular reservoir s'urroundingtheelectrode and defined by the insulating sleeve or collar 212 mountedwithin the lower 'end' of the barrel-209. However, be-

cause of the presence of the insulating collar 212, a direct electricalpath from the electrode 164 to the'barrel 209 or ring 211 through themolten lead 214 is precluded. v 1

Further downward movement of the ram 205 and electrode 164 now serves tomelt the remainder of the upstanding locating collar 159 on connector151, as well as the upper portion of flange 155 on bushing 149, thuscreating a condition as best illustrated in FIG. lld. The system may bereadily adjusted (in a manner more specifically described in theaforesaid application of Raymond L. Schenk,';lr., Ser. No. 435,178,filed .Ian.

21, 1974) to provide for penetration of the electrode 164through thebond area to any desired and preselected depth within the workpieces.When the desired depth has been reached a limit switch LS-1'(FIG. 5)will be actuated by means of an actuator 215 carried by the ram, andsuch actuation will serve to initiate a short time delay period duringwhich the electrode 164 will dwell in its advanced position as shown inFIG. 11d with bond power on, thereby insuring that'the'un-' meltedportions of battery post 148, bushing 149 and connector 151 areuniformly heated, and at the same time serving to insure that the moltenlead 214 main tained within the reservoir is also uniformly heated. Atthe conclusion of the time delay period, the ram 205 and electrode 164are retracted, while the barrel 209 of the ram assembly 146 is left inits downward position as best shown in FIG. lle. In this position, themolten lead 214 is permitted'to return to the cavity formed in theworkpieces by advancemovement of the electrode, and such molten materialis thereafter permitted to cool and solidify during a preset coolingcycle. Upon completion of the cooling cycle, the barrel 209 of the ramassembly is retracted and the bonding cycle is complete.

C. C arbon-Graphite Electrode In the practiceof the present invention ithas been found that the electrode 164 may be made ofa wide variety ofmaterials and in various configurations dependent upon the nature of thematerial being bonded and the desired characteristics of the finishedbond. Merely by way of example, it has been found that satisfactoryresults can be obtained in some applications by utilizing an electrodeformed of stainless steel or the like. However, when utilizing thepositive displacement casting system of the present invention to formbattery post/- connector bonds, stainless steel has proven less thandesirable in a number of respects. The difficulties that have beenencountered are believed to be related to the particular material beingbondedviz., lead-to-lead bonds. That is, it is generally known that leadhas a particulartendency to oxidize, and this problem is rendered evenmore serious by the fact that it is common practice in the batteryindustry to use antimony-lead and, in some instances, calcium-lead,materials. For example, antimony is commonly added to the lead to impartgreater strength. It has been found that when bonding, for example,antimony-lead with the present invention, there is a tendency for theantimony to oxidize and plate'out on the electrode 164, particularlywhere the electrode is made of stainless steel. Such plating out ofantimony, and/or accumulation of other lead oxides onthe electrode,tends to significantly decrease the useful life of the electode,necessitates continual' removal and cleaning of the tip, and leads toundesirable arcing as the oxides accumulate on theelectrode,often'leading to destruction 'of the lead battery components.7

To overcome the foregoing problem, provision is made for takingadvantage of the unique properties of carbon-graphite as an electrodematerial. Thus it is known that carbon-graphite is characterized by com-'bining high thermal conductivity characteristics with high electricalresistivity characteristics, thereby permitting lower current flow andattainment of a more uniform temperature profile for an electrode ofgiven geometry than theretofore possible. However, prior to the presentinvention, carbon-graphite has not proven satisfactory for a bondingelectrode material, primarily because such prior systems have normallydepended upon a combination of elevated temperatures and pressure toachieve a desired bond, and carbon-graphite simply was not suitable'forwithstanding the repetitive impacts involved between workpieces and theelectrode, particularly at the high pressures imparted between theparts.

With'the present invention, however, it is now possible to obtain soundelectrical and structural bonds between lead .workpieces or the likewithout having to exert great pressure-indeed, the present invention

1. An improved method for molecular fusion bonding of a battery post toan intercell connector in a lead-acid motive-power battery comprisingthe steps of: a. positioning the battery with the lead battery postextending vertically upward through the battery cover along a work axis;b. positioning a lead intercell connector in coaxial surroundingrelation to the lead battery post; c. positioning a bonding head havinga ram and a coaxial barrel over the battery with the ram disposed on thework axis; d. forming an annular depending rib surrounding a workreceiving recess on the work-engaging face of the end of the ram; e.moving the ram and barrel into engagement with the battery post andintercell connector, respectively; f. heating the ram to a temperaturesufficient to convert the lead components in the path of ram movement tothe molten state; g. moving the heated ram through the barrel andaxially through the battery post and the inner peripheral edge of theintercell connector with the annular work-engaging surface on the ramfollowing the post downwardly as the latter melts and displacing themolten lead thus formed upwardly into the barrel in surrounding relationwith the ram; h. retracting the ram from engagement with the unmeltedlead components and the molten lead; i. returning the molten leadtheretofore displaced into the barrel back to the area of rampenetration into the battery post and intercell connector where suchmolten lead is permitted to cool and solidify; j. retracting the barrelfrom the intercell connector upon cooling and solidification of themolten lead.
 2. A method as set forth in claim 1 wherein said batterypost passes coaxially through an annular bushing molded into the batterycover and wherein the intercell connector is provided with a verticalopening positioned in coaxial surrounding relation to an upstandingflange on said bushing, further characterized in that the ram isdimensioned slightly larger than the opening in said connector and saidannular work-engaging surface is dimensioned to engage and penetratesaid bushing flange.
 3. Apparatus for bonding n meltable component partstogether by a positive displacement molecular fusion bonding process,said apparatus comprising, in combination: a. means for supporting saidn meltable component parts on a work axis; b. a frame; c. a bonding headcarried by said frame in a position overlying the component parts; d. abarrel carried by said bonding head for movement along said work axisinto sealing engagement with the component parts to be bonded; e. a ramcarried by said bonding head for movement along said work axis, said rambeing coaxial with said barrel and capable of axial movementtherethrough; f. an electrode mounted on the work-engaging end of saidram, said electrode having an annular depending rib surrounding a workreceiving recess formed coaxially on its work-engaging face; g. meansfor advancing said barrel and said electrode into engagement with saidcomponent parts; h. means for heating said electrode to a temperaturesufficiently high to melt and form a cavity in those portions of thecomponent parts in the path of ram movement; i. ram advancing means forpositively displacing the molten material formed by engagement of saidheated electrode with the component parts into said barrel and storingthe molten material therein in heat transfer relation with said heatedelectrode; j. means for axially retracting said ram and said electrodefrom said component parts so as to enable the displaced molten materialstored in said barrel to flow back to said cavity where said material ispermitted to cool and solidify to form a uniform molecular fusion bondbetween said component parts with said bond being coextensive with thedegree of penetration of said ram into said component parts; and k.means for axially retracting said barrel from engagEment with saidcomponent parts following cooling and solidification of said moltenmaterial.
 4. Apparatus as set forth in claim 3 futher characterized inthat said rib is disposed adjacent and slightly inboard of theperipheral side edge of said electrode.
 5. Apparatus as set forth inclaim 3 further including means formed on the upper face of saidelectrode opposite said work-engaging face for removably attaching saidelectrode to electrode driving means.
 6. An electrode set forth in claim5 in which said removable attaching means comprises a screw-threadedconnector element.